This invention relates to improvements in a system for generating a command speed signal providing a reference for controlling the speed of a moving member.
Moving members and more particularly elevator cars are operated by controlling the speed thereof in accordance with a speed reference pattern in order to provide a comfortable ride therein and improve the accuracy with which the cars are stopped at their desired positions. There are already known command speed signal generators of the type comprising three resistors serially interconnected across a source of direct current, and a series combination of a plurality of sets of normally open contacts connected across a first one of the resistors with the junctions between the contact sets connected to respective taps on the first resistor. The contact sets are responsive to a command acceleration signal to shortcircuit the first resistor in an incremental manner to produce across a third one of the resistors a voltage which is increased stepwise to a predetermined magnitude. After having been smoothed, the voltage is used to start and accelerate an associated elevator car and is maintained at the predetermined magnitude to cause the car to travel at a predetermined fixed speed. When a command deceleration signal is applied to the traveling car, the contact sets are successively opened to insert the first resistor into a circuit in an incremental manner to produce across the third resistor a voltage which is decreased stepwise to a null magnitude for stopping the car.
Since elevator cars should desirably be operated in acceleration and deceleration modes which have different characteristics from each other, it has not been easy to satisfactorily control both the acceleration and deceleration modes of operation by the contact sets as above described. Therefore it has been difficult to produce a command speed signal providing an ideally comfortable ride in elevator cars.
Accordingly it is an object of the present invention to provide a new and improved system for generating a command speed signal to provide a comfortable ride in a moving member such as an elevator car.